Barometric stack dilution device



Nov. 8, 1960 H. FRIEDBERG 2,959,139

BAROMETRIC STACK DILUTION DEVICE Filed Aug. 2, 1955 2 Sheets-Sheet l FF 3 b INVENTOR. Harry fi'iedberg ATTORNEYS 2 Sheets-Sheet 2 Nov. 8, 1960 H. FRIEDBERG BAROMETRIC STACK nmmom DEVICE Filed Aug. 2, 1955 INVENTOR. Harry fi'ledbelg BY A%6/4 zza/wf 4907M ATTORNEYS BAROMETRIC STACK DILUTION DEVICE Harry Friedberg, Cleveland, Ohio, assignor to Waste King Corporation, a corporation of California Filed Aug. 2, 1955, Ser. No. 525,955

3 Claims. (Cl. 110-18) This invention relates to improvements in an incinerator and more particularly to a barometric stack dilution device for controlling the rate of combustion and flue pipe temperatures in incinerators.

One of the objects of the present invention is the provsion, in combination with a combustion chamber and an exit flue therefrom, of means forming an unobstructed passageway between atmosphere and the zone in the exit flue closely adjacent the combustion chamber, said passageway having a flow resistance which is approximately equal to the predetermined desirable flue draft at the exit flue end of the combustion chamber under full capacity operation thereof.

Another object of the present invention is the provision in a domestic incinerator having a combustion chamber with an inlet for combustion air ingress near the top of the chamber and with the combustion products exit flue communicating between the chamber and a source of draft pressure, of an open passageway between atmosphere and the zone in the flue closely adjacent the combustion chamber calculated to hold the effective draft at the exit flue to a value where combustibles are substantially completely burned in the chamber.

Another object of the present invention is the provision in a domestic incinerator having a combustion chamber with an inlet for combustion air ingress near the top of the chamber and the combustion products exit flue leading generally horizontally out of the upper portion of the chamber and communicating with the source of draft pressure, of a flame impingement plate positioned in the exit flue and spaced from its top wall to provide a by-pass which communicates at one end with the upper portion of the combustion chamber and at its other end with the source of draft pressure, so that a small amount of inlet air may move directly through the by-pass and out to the stack so as to cool the exit flue near the chamber in case unusually high draft causes flames to enter the flue pipe system.

Other objects and advantages of the present invention will appear from the accompanying drawings and description and the essential features thereof will be set forth in the appended claims.

In the drawings,

Fig. 1 is a side elevational view of an incinerator equipped with my improved device;

Fig. 2 is an end elevation of the same taken from the right-hand end of Fig. 1;

Fig. 3 is a top plan view of the device shown in Figs. 1 and 2; while Fig. 4 is a transverse sectional View, enlarged, taken along the line 4-4- of Fig. 3.

This invention is directed toward the problem of excessive combustion rates in domestic incinerators. High combustion rates in such incinerators result in incomplete combustion in the combustion chamber itself so as to cause a portion of the burning gases to be drawn into the flue pipe or stack so that further combustion takes place in the flue pipe. Under such circumstances, flue pipes States Patent f Patented Nov. 8, 1960 are often heated to incandescence producing high radiation temperatures which are undesirable and hazardous to the surrounding premises.

The present invention attacks the above problem by holding down the combustion rate by means of control of the negative draft pressure in the flue pipe to a predetermined maximum; and by cooling the flue gas through cold air dilution.

The entry of combustion air into the combustion chamber can take place only as rapidly as the products of combustion are removed. Hence, within limits, the amount of combustion air entering a combustion chambet is a direct function of the draft in the flue pipe or stack. The air ingress into the combustion chamber should only be sufficient in volume to complete all of the combustion within the chamber itself. This will result in a complete oxidation of the products of combustion so that odors are kept to a minimum and free carbon and ash in the flue gas products are kept at a minimum also.

When the flue draft exceeds a desirable maximum, the products of combustion are rapidly removed and pulled over into the fine pipe. At the same time, equivalent quantities of combustion air enter the combustion chamher. The rate of combustion then increases progressively until the rate becomes so great that unburned and burning gases are drawn into the flue pipe system where combustion continues. This condition is extremely undesirable as it produces high flue pipe temperatures detrimental to the flue pipe system and to the surrounding premises.

The present invention provides a means for holding the neagtive draft pressure to a predetermined desirable maximum at the point where the exit flue leads from the combustion chamber. The present invention is effective for this purpose under all conditions except that of exceptionally heavy draft at which time further air dilution is provided along the top of the flue pipe to hold down the temperature there.

It is well known that barometric control devices have been made and sold to control the stack draft and to limit the maximum to a predetermined value. These usually consist of a balanced shutter or butterfly valve separating the flue pipe from the surrounding atmosphere. The balanced shutter remains closed until a difference in static pressure between the flue draft and the atmosphere reaches a predetermined value, thus overcoming the action of the balancing means of the shutter and permitting the shutter to swing open. Upon such opening, direct entry of room air into the flue pipe occurs, thus lowering the total draft at the outlet of the incinerator.

The inherent faults of such barometric control devices are undesirable leakage, shutter inertia making the devices overly sensitive, inadequacy of shutter trunnion bearings and short lift of the same if the control device is near the incinerator, fly ash exhausted from the incinerator under periods of great draft fluctuation, and inability of the device to respond to down draft conditions.

Draft leakage is inherent in the design of such barometric control devices because in order to make the shutter a swing freely, responsive to stack draft variations, the shutter must be loosely mounted, thus making it impossible for the shutter to completely close off the opening in which it is mounted. During periods of low draft conditions, such leakage is sufiicient to completely nullify the draft at the incinerator. Since domestic incinerators are often installed where the normal stack draft is between .01 inch and .02 inch water gauge, the leakage through the barometric control devices under such circumstances will completely nullify the stack draft.

from high temperatures they are used in positions remote from the flue pipe exit from the incinerator chamber. When used at such a remote point, the flue pipe between the incinerator and barometric control device becomes too hot for safety.

The present invention provides an answer to the above problem by an arrangement which has no moving parts, which has no effect upon the draft at the incinerator under low draft conditions and which automatically dilutes the products of combustion in the flue pipe with cool outside air entering at a point very close to the incinerator chamber.

One such device is shown in the accompanying drawings. It will be understood that the details of the incinerator combustion chamber shown here are for illustration only as my device can be attached to any such incinerator. The device here shown comprises an incinerator chamber which is bounded by the walls 11 outside of which are insulating air passageways 12 which provide an inlet for combustion air ingress to the chamber 10. Referring to Fig. 4, inlet opening means 13 is provided through the bottom plate 14 of the incinerator in registration with the upwardly extending passageways 12 so that air for combustion may enter here and pass upwardly around the walls 11 so as to keep the outer housing 15 of the incinerator cool. As an additional precaution, heat insulation 16 is provided along the side walls and top of the incinerator. In the top Wall 17, a suitable opening 18 is provided for the introduction of rubbish or combustibles into the incinerator and this is normally closed by a removable cover 19. The combustible material is usually supported upon a grate 20 which is provided with means for shaking the same as indicated at 21. Below the grate is an ash drawer 22 which is adapted to slide in and out of the incinerator on a false bottom 23. Preferably, but not necessarily, an open-work grille 24 is provided near the back wall of the incinerator to maintain a free passageway 25 for the products of combustion to the exit flue pipe 26 which extends generally horizontally out the back Wall of the incinerator near the top thereof. It will be understood that the member 27 is merely a brace for attaching the grille 24. Suitable burner means is indicated at 28 for burning the combustibles and the particular details of this burner form no part of the present invention.

My invention comprises the provision of an unobstructed passageway 29 of fixed size between the atmosphere and the zone in the flue pipe 26 closely adjacent the combustion chamber 10. In the present embodiment, designed for a combustion chamber adapted to hold approximately two bushels of combustible material, the passageway 29 is generally rectangular in section having a dimension A parallel to the back wall of the incinerator of 6 7 inches inside. The dimension B at right angles thereto is approximately 1% inches inside, thus giving a cross-sectional area of approximately 7.734 square inches to this passageway 29. In the preferred form of my invention, an enlarged chamber 30 is provided at the atmospheric end of the passageway 29. In the embodiment shown, this chamber 30 has the same dimension parallel to the back Wall of the incinerator as the passageway 29, namely, 6%; inches inside. The dimension C at right angles thereto is 4 /2 inside giving a cross-sectional area in this enlarged chamber 30 of 27.87 square inches. The vertical dimension D of the chamber 30 is approximately 6 inches inside. The lower end of the passageway 29, 30 is open to atmosphere at 31. In the present embodiment, this opening 31 is generally rectangular measuring 1% inches (E) by 6 7 inches (A) inside. The dimension F from the lower end of chamber 30 to the center line of the flue pipe is approximately 18 inches. The flue pipe 26 is about 6 inches inside diameter. Preferably, an upstanding lip 32 is provided which in the present embodiment is about one inch high, extending vertically upward from the bottom wall of the chamber 30 immediately along the incinerator side of the opening 31 and extending entirely along the 6 inch dimension thereof. The purpose of this lip is to aid in the creation of turbulence and to increase the resistance of air flowing from the opening 31 through the passageway to the flue pipe 26 and to act as an ash trap.

It will be noted that air moving upwardly through the passageway 29, 30 from the opening 31 to the flue pipe 26 must make three ninety degree turns or changes in direction of flow. These changes in air flow direction, the turbulence created by the lip 32, and the calculated length and cross-sectional area of the flow passageway, are arranged to cause a flow resistance amounting to approximately .025 inch to .030 inch water gauge. The resistance to flow may be increased by extending the lip 32 upwardly or by the addition of other baflies. This has not been found necessary.

In operation, air for combustion passes upwardly in the passageways 12, enters the combustion chamber 10 at 33 giving a down draft combustion to the material in chamber 10 as ignited by the burner 28. The products of combustion pass in the direction of the full line arrows out the flue pipe 26 which, it will be understood, is connected to a source of draft pressure such as a stack or the like. Little or no air for dilution of the products of combustion with atmospheric air enters the flue pipe 26 through the open passageway 29, 30 until the stack draft is in excess of .025 inch to .030 inch (as designed) because that much air pressure is required to overcome the resistance of the open passageway at low rates of flow. Experience has taught that at draft pressures of .030 or less, combustion in the incinerator chamber 10 is sufflciently slow so that it is completed within the combustion chamber and practically none takes place in the flue pipe 26. At .030 inch of draft in the flue pipe 26, temperatures are comparatively low and safe. However, when the flue draft exceeds .030 inch water gauge, the resistance of the passageway 29, 30 to air flow is overcome and dilution air moves up the passageway from opening 31 into the flue pipe 26, cooling the flue pipe and its gases over the flues entire length, reducing the flue pipe and gas temperatures to a safe level.

A typical example of the operation of this device was recorded as follows:

Draft Pressure in Incinerator at Entrance Draft Pressure Draft Pressure to Flue Collar at 31 in Flue 26 .008" Water Column .0 .009 .010 .0 .012 .015 .005 .032 .02 .03 5 .058 .025 .04 .07

It will be understood that the above draft pressures are negative pressures below atmospheric. The above values are typical and were recorded during fire hazard test conditions. It will be noted that the incinerator draft was held within reasonable values and my improved barometric stack dilution device permitted sufficient air to enter the flue pipe to make up approximately the difierence between the incinerator draft and the flue draft.

An additional improvement which may be added to my invention is indicated at the by-pass 34 which is provided by means of a flue impingement plate 35 which is arcuate in form as clearly seen in Fig. 2 and spaced from the top wall of the flue pipe 26. The dimension G is approximately inch inside dimension. This by-pass communicates at the left end, as viewed in Fig. 4, with the upper portion of the combustion chamber 10, and

' at its right-hand end with the source of draft pressure.

travel directly beneath the top wall of chamber into the by-pass 34 and along this by-pass so as to put a cooling blanket between the hot gases'in the flue and the top wall of the flue pipe 26. Without this improvement, under the conditions indicated, the flue pipe in close proximity to the incinerator could be heated to as high a temperature as a dull cherry red color. It will be noted that the impingement plate 35 is located at approximately the point where the combustion gases coming out of chamber 10, as indicated by the full line arrows, would normally strike the top of the flue pipe. It will also be noted that the impingement plate 35 is diametrically opposite the opening where passageway 29, communicates with the flue pipe 26.

I have thus provided a device which has practically no eflfect upon the draft exerted at the exit of the incinerator flue under draft conditions under a predetermined minimum. As the draft increases above this predetermined minimum, the effect of my draft dilution device is to hold the draft at the outlet of the incinerator approximately constant while automatically diluting the hot combustion gases with cold atmospheric air. Devices constructed according to the teachings of this invention, have been proven by test to hold the temperature of the flue pipe 18 inches from the exit, to a temperature not over 90 degrees Fahrenheit greater than the atmospheric temperature.

What I claim is:

1. In a domestic incinerator having a combustion chamber with an inlet for combustion air ingress near the top of said chamber and with a combustion products exit flue leading generally horizontally out of the upper portion of said chamber and communicating with a source of draft pressure; the combination therewith of a flue impingement plate positioned in said exit flue and spaced from its top wall to provide a by-pass there, said by-pass providing an elongated passageway several times as long as said spacing of said plate from said top wall, said bypass passageway being substantially separated from said flue except for its end openings, said by-pass communicating at its one end with the upper portion of said chamber below said inlet for combustion air ingress and on the exit flue side of said inlet and at its other end with said source of draft pressure, whereby a small amount of inlet air may move directly through said by-pass and thence out said exit flue.

2. In a domestic incinerator having a combustion chairiber with an inlet for combustion air ingress near the top of said chamber'and with a combustion products exit flue leading generally horizontally out of the upper portion of said chamber and communicating with a source of draft pressure; the combination therewith of a flue impingement plate positioned in said exit flue and spaced from its top wall to provide a by-pass there, said by-pass providing an elongated passageway several times as long as said spacing of said plate from said top wall, said bypass passageway being substantially separated from said flue except for its end openings, said by-pass communicating at its one end with the upper portion of said chamber below said inlet for combusition air ingress and on the exit side of said inlet and at its other end with said source of draft pressure, whereby a small amount of inlet air may move directly through said by-pass and thence out said exit flue, and means forming a substantially unobstructed passageway of fixed size between atmosphere and the bottom of said flue closely adjacent said chamber, and opposite said impingement plate, said passageway being of a cross-sectional flow area holding the effective draft at said exit flue to a maximum of approximately .030 inch water gauge when said source of draft pressure varies from zero to approximately 0.15 inch water gauge.

3. An incinerator as in claim 2 wherein said unobstructed passageway has a vertically extending portion of predetermined cross-sectional area communicating with the bottom of said flue, and at the lower end of said vertical portion, an enlarged portion surrounded by walls, there being a continuous wall at the bottom of said enlarged portion and vertically directly below said vertically extending passageway portion, there being an opening from the atmosphere into said enlarged portion laterally to one side of said continuous bottom wall portion, said opening being the sole opening leading into said unobstructed passageway.

References Cited in the file of this patent UNITED STATES PATENTS Re. 19,102 Dibble Mar. 6, 1934 189,006 Yon Mar. 27, 1877 1,311,522 Jones July 29, 1919 1,717,851 Pence June 18, 1929 2,702,012 Weggel Feb. 15, 1955 2,711,139 Martin June 21, 1955 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2,959, 139 November 8, 1960 Harry Friedberg It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2 line 32 for neagtive" read negative line 54c for "lift" read life line 59, strike out. "a"; column 6, line 14L for "combusition" read combustion line l5 after exit" insert flue Signed and sealed this 2nd day of May 1961.

(SEAL) Attest: ll-

ERNEST W1, SWIDER DAVID Lo LADD Attesting Officer Commissioner of Patents 

